Composite piezo-electric torsion device



Nov. 2 6, 1929. A. McL. NICOLSON 1,737,019

COMPOSITE PIEZO ELECTRIC TORSION DEVICE Filed Dec. 20. 1926 INVENTOR ALEXANDER MtLEAN NICOLSON BY W A'TTQENEY 2 Patented Nov. 26 1929 ll 3 UNITED STATES PATENT OFFICE ALEXANDER MCIIEAN NICOLSON, OF NEW YORK, N. Y., ASSIGNOR TO WIRED RADIO, INCL, OF NEW YORK, N. Y., A. CORPORATION OF DELAWARE COMPOSITE PIEZO-ELE CTRIC TORSION DEVICE Application filed December'SZO, 1926. Serial No. 155,899.

This invention relates to piezo-electric crystal devices more particularly adapted and arranged to be utilized in connection with electric circuits and to a method of producing the same. It has been known for some time that crystals of certain substances, such as Rochelle salt, quartz, tourmaline, and the like, produce an 'electro-motive force if subjected to physical stress or movement, and conversely, produce physical stresses or movement in response to the impression of an electro-motive force upon them.

Such crystals are capable of wide use and application in theelectrical arts, and particularly in those arts which deal with the generation, transmission, andutilization of alternating currents or potentials, whether of audible frequency or of the highest radio frequency.

In my Patent No. 1,459,429 issued May 27, 1924, I have shown that Rochelle salt piezoelectric crystals may be used in the generation of electrical oscillations;

In the past, difficulties have been encountered in the use of comparatively large crystals and crystals made by growth from a solution of the mother liquor, such as Rochelle salt crystals. The large crystals, as will be understood, require more time to grow than the small ones, and moreover, they seem to be considerably more fragile and tend to develop cracks and flaws even before the crystals have been effectively cured and hardened.

In the case of natural crystals, such as uartz and tourmaline, etc., it is clear that t e difliculty and expense of preparing crystals increases greatly with the size, and the liability of accidental injury in the use of the .crystal is much greater.

It is an object of this invention to provide a composite piezo-electric cr stal, particularly adapted for torsional vi ration, and a 7 method of producing the same, Whereb the crystal may be given any desired size, s ape, and natural frequency, by utilizing frag ments of crystals, small crystals, crystal nuclei, and the like, of heterogeneous size and shape, physically secured together to form a single entity and provided with electrodes so that the piezo-electric effects of the coma It is stlll a further object of this invention to provide an improved piezo-electric device of high efficiency and relatively low cost, and one which may be relatively quickly produced. Still other objects of this invention will be apparent from the specification.

The features of novelty which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental princi les and as to its practical. application, will best be understood by reference to the specification and accompanying drawing, in which:

Fig. l is an elevation partly in section of a composite piezo-electric device according to my invention,

Fig. 2 is a diagrammatic view showing one way of assembling the component crystals 1nto a composite structure,

Figs. 3-6 are plan views in section of a composite device according to my invention assembled in different ways.

In accordance with m invention, I select a multiplicity of piezo-ellectric -crystals to be assembled into a composite device. The selection is preferably made by choosing crystals which are chemically and optically similar. For example, I may select a number of quartz crystals, being careful to separate the crystals of dextro as mmetry from those of laevo asymmetry. T e composite piezoelectric device may be constructedof either of the components, but it is preferable to use in any one composite assembly only crystals of the same asymmetry, as otherwise themechanical vibrations of the one class will be mechanically 180 out of phase with those of the other class, which will interfere with the proper functioning of the device, and may even cause its destruction.

In the case of other hemihedral crystals which occur only in right-handed or lefthanded forms, such .for example as Rochelle salt, the step of separating the forms is clearly not necessary.

After the component crystals have been selected, I may then proceed to build up a composite structure by arranging the crystals in the desired fashion, bein careful to orient each crystal properly wit respect to the c-axis so that the piezo-electric effects of .the various component crystals may be integrated. Since crystals of like chemical and optical form are always analogous to either a right-handed screw thread, or a left-handed I screw thread, depending on whether the crystals are dextro or laevo asymmetrical, it suffices merely to arrange the crystals with their c-axes parallel, and with symmetrical electrodes, for applying or drawing electricity from the component crystals;

The electrodes may comprise plates or metal foil secured to the crystals at proper points forming mechanically and electrically opposite poles. For example, one electrode may comprise an equatorial belt of conducting material forming a loop around the. .orystal in a plane normal to the c-axis, and

the other electrode may be attached to the basal plane of the crystal, as more'particularly descrlbed in the applications referred to above.

Observing this requirement, ,the component crystals may be assembled into a composite structure in a number of wa s. Referring now more particularly to ig. 1, I have shown a number of crystals 1, 2, 3, 4, etc.,'assembled into a more or less cylindrical structure, in which there are arranged a number of crystals in line with the c-axis which is shown as a dot and dash line. The component crystals herein shown are arranged in any desired manner so as to build up a composite structure of the desired dimensions, by the juxtaposition of the various crystals.

The various component crystals may be secured together physicall into a single entity in any desired manner, ut I prefer to use a cement of the same elastic roperties as those of the component crysta s, so that stress waves will be transmitted to all of the comas? 1" I prefer to use what I term Rochel e salt ponents. In the case of Rochelle salt cr stals,

cementwhich is described in my Patent No. 1,638,830 issued July 26, 1927., for Rochelle salt composition, or a melt of Rochelle salt which has been melted at a temperature controlled according to the amount of water of crystallization it is desired to retain in the melt.

After the composite crystal has been formed, herein shown as a cylinder, it may and rigidly secured thereto, as by cementing.

In addition, a plurality of mechanical clamping means, such as flexible tie rods 50 and 51, may be provided passing through the base and on threaded to receive nuts 52 and 53 by whichthe crystal structure may be put under com ression. The crystal is now ready for use, an may function either as a generator or motor. That is to say, electromotive fluctuations may be impressed upon it, which will be converted into torsional vibrations of the 30 crystal, such that one end of the cylinder tends to rotate with respect to the other end, or physical stresses may be a plied to the crystal tending to rotate one en in a plane normal to the c-axis, in order to produce fluctuations of electromotive force corresponding. thereto.

Referrin now to Fig. 2, I'have shown a more regu ar arrangement of component crystals. In this instance one row of crystals may consist of crystals 10, 11, 12, and 13 all arranged with their c-axes parallel, and being arranged in lines normal to the c-axes. It will be understood that a plurality of crystals may be arranged also in the same plane with crystals 10, 11, 12, and 13, but normal to the 5 line of those crystals, thereby forming a solid structure in which there are a plurality of crystals arranged in lines normal to the c-axis and normal to each other as illustrated more clearly in Fig. 1. A second layer of crystals 14, 15, and 16 may be disposed above the first layer, and an additional layer of crystals 17, 18, 19, and 20 may be arranged. More layers may be added as desired, with the object of bringing the composite structure to the dimensions desired, corresponding electrodes (shown diagrammatically) being provided whereby corresponding poles on the component crystals may be connected together, as for example by means of leads 21, 22, 23 and 24 connected to main lead 28, on the one hand, and leads 25, 26, and 27, connected to main lead 29.

It will be understood that if mechanical stress be applied to the crystal structure of 1 5 Flg. 2 so as to torsionall'y stress vthe crystal about the o-axis, an electromotive force will manifest itself upon leads 28 and 29, and conversely, the application of an electromotive force to these leads will cause a corresponding stress of the composite crystal.

Referring now to Figs. 3-6, which are sec tional views taken on planes normal to the c-axis of the component crystals, I have shown additional ways of arranging the various component crystals so that plezo-electrio effects of the component crystals may be integrated. In Fig. 3, it will be noted, the crystals 33 and 34 are arranged in a symmetrical arrangement, the remaining space being partially or completely filled by the binder such as cement or nielt 35, if desired.

The arrangement in Fig. 4 is symmetrical, comprising crystals 36-43, and the remaining space being taken by the binder 35 as before. In the arrangement shown in Fig. 5, the various crystals ,45,, are arranged in a ring, the internal and external space being filled by the binder 35.

The arrangement shown in Fig. 6 is a heterogeneous arrangement of crystals 46 46 4:6,, of varying sizes and shapes, the interstices being occupied by the binder 35.

While I have shown and described certain preferred embodiments of my invention, it Will be understood that modifications and .changes may be made without departing from the spirit and scope of my invention, as will be understood by those skilled in the art.

I claim:

1. A composite Rochelle salt piezo-electric crystal adapted for torsional vibration comprising a multiplicity of component Rochelle salt piezo-electric crystals chemically and optically similar of heterogeneous size and shape secured together with their c-axes parallel by a physically continuous body, said crystals being so connected that piezo-electric torsional vibration of said individual components may be integrated. I 2. A composite Rochelle salt iezo-electric crystal adapted for torsional vi ration comprising a plurality of component Rochelle salt piezo-electric crystals secured together with their c-axes parallel by a physically continuous body and by metallic clamping means embracing a plurality of said crystals, said crystals being disposed in parallel planes and so connected that piezo-electric torsional vibrations of said individual components may be integrated.

3. A composite Rochelle salt piezo-electric crystal adapted for torsional vibration, comprising a multiplicity of component Rochelle salt piezo-electric crystals chemically and optically similar, of heterogeneous size and shape, secured together with their c-axes parallel by a physically continuous body, and

oriented with respect to each other in planesnormal to the c-axes and so connected that piezo-electric torsional vibration of said individual components may be intergrated.

4. A composite Rochelle salt piezo-electric crystal adapted for torsional vibration, comprising a multiplicity of component Rochelle salt piezo-electric crystals having torsionally vibrating characteristics chemically and optically similar, of heterogeneous size and shape, and a pair of members for securing said crystals in stacked relation, with the c-axes of the components parallel, said crystals being so connected that piezo-electric torsional vibrations of said individual components may be integrated.

5. A composite Rochelle salt piezo-electric crystals adapted for torsional vibration comprising a base plate, an end plate, a plurality of Rochelle salt piezo-electric crystals physically secured together with their c-axes parallel in superimposed relation between said plates by flexible metallic clamping means extending between said plates, said crystals being so connected that piezo-electric torsional vibrations of said individual components may be integrated.

6. A composite Rochelle salt piezo-electric crystal adapted for torsional vibration, comprising a multiplicity of component Rochelle salt piezo-electric crystals chemically and optically similar, of heterogeneous size and shape, with the c-axes of the component crystals parallel and with a plurality of crystals in line parallel to said axis, secured together by a physically continuous body, and so connected that piezo-electric torsional vibrations of said individual components may be integrated.

7 A composite Rochelle salt piezo-electric crystal adapted for torsional vibration comprising a plurality of chemically and optically similar Rochelle salt piezo-electric crystals superimposed one upon another, with their c-axes parallel, metallic clamping means engaging the end crystals of said superimposed crystals, said crystals being so connected that piezo-electi'ic torsional vibrations of said individual components may be integrated.

8. A composite Rochelle salt piezo-electric crystal adapted for torsional vibration, comprising a multiplicity of component Rochelle salt piezo-electric crystals chemi cally and optically similar, of heterogeneous s1ze and shape, with the c-axes of the component crystals parallel and with a plurality of crystals in line parallel to said axis and normal thereto, secured in superimposed relation and so connected that piezo-electric torsional vibrations of said individual components may be integrated.

9. A composite Rochelle salt piezo-electric crystal adapted for torsional vibration, comprising a multiplicity of component Rochelle salt piezo-electric crystals chemically and optically similar, of heterogeneous size and shape, with the c-axes of the component crystals parallel and with a plurality of crystals in line parallel to said axis and normal thereto, and cemented togther by cement having elastic properties similar to those of said component crystals and so connected that piezo-electric torsional vibration of said individual components may be integrated.

10. A composite Rochelle salt piezo-elec tric crystal adapted for torsional vibration comprising a plurality of chemically and optically similar Rochelle salt iezo-electric crystals in superimposed stacke relationship with their c-axesparallel and with a plurality of crystals in line parallel to said axis and normal thereto, by elastic clamping means engaging said crystals, said crystals being so connected that piezo-electric torsional vibrations of said individual com- Y ponents may be integrated.

1o 11. A composite piezo-electric crystal adapted for torsional vibration, comprising a multiplicity of component piezo-electric crystals characterized by having torsionally vibrating properties and being chemically and optically similar, of heterogeneous size and shape, with the o-axes of the component crystals parallel and with a plurality of crystals in line parallel to said axis and normal thereto, said crystals being cemented together by a cement having elastic properties similar to those of said component crys-. tals, and so connected that piezo-electric torsional vibrations of said individual components may be integrated.

12. A composite piezo-electric device adapted for torsional vibration comprising a multiplicity of component piezoelectric crystals characterized by having torsionally vibrating properties and being chemically so and optically similar of heterogeneous size and shape, means for. securing said crystals in superimposed relationship, cement having elastic properties similar to those of said component crystals com rising means for uniting said crystals, wit the c-axes of the component crystals parallel, the faces of abutting crystals being so connected that piezo-electric torsional vibrations of said individual components may be integrated, and

4 means for applying compression to said composite device.

13. A composite piezo-electric device adapted for torsional vibration comprising a multiplicity of component piezo-electric cr stals characterized by having torsionally vi ratin'g properties and being chemically and optically similar, of heterogeneous size and shape, a cement having elastic properties similar to those of said component crystals for uniting said crystals in superimposed relationshi with the a-axes of the component crysta s parallel, the faces of said crystals being so connected that iezo-electric torsional vibrations of said in ividual components may be integrated, and means forapplying compression to said composite device along the line of the c-axis of the component crystals.

In testimony whereof I hereunto aflix my signature.

ALEXANDER MGLEAN NICOLSON. 

